Gladiator Ghosts appear in the episode "Morituri Te Salutamus." The known names of the gladiators are Hyperion and Primo, Priscus and Verus, Amazonia and Achillea, Triumphus, Rutuba, Tetraides, and Romulus and Remus. When they were alive they were forced by the Fight King to fight other ghost gladiators and then eventually each other. As Finn and Jake fought them they were screaming cries for forgiveness and the names of the friends they killed or were killed by. After Finn killed the Fight King by shattering his sword, the ghosts were freed and ascended into the sky in pairs, followed by the arena they were imprisoned in.
The ghosts appear to look as they were when they died, including one who is decapitated. Some of them seem to be composed of two people melded together, as with the two-headed gladiator Romulus & Remus.
- Several of the names of the Gladiator Ghosts in "Morituri te Salutamus" are taken from famous gladiators in history and fiction:
- Amazonia and Achillea were female gladiators whose graves were discovered in London.
- Priscus and Verus were gladiators known to fight at the opening games of the Flavian Amphitheatre.
- Flamma was a famous gladiator in Roman history.
- Rutuba is a gladiator mentioned in the Satires of Horace.
- Tetraides is a fictional gladiator from the book The Last Days of Pompeii, by Edward Bulwer-Lytton.
- Romulus and Remus are the legendary brothers who supposedly founded Rome, where gladiators originated.
- Hyperion is a Titan in Greek Mythology, and is Greek for "The High-One."
- Primo means "first" in Latin.
- Triumphus means "the triumph of" in Latin.
- According to Andy Ristaino, all the Gladiator Ghosts are homosexual. It can be noted that one of the ghosts calls the one he killed his love.
- When Priscus disappeared, he said "Et tu Verus?," a reference to Caesar's dying words, "Et tu, Brute?" In Latin, it means "You too, Verus?"
- Romulus and Remus' sword bears heavy resemblance to the swords used by the Uruk Hai warriors from the Lord of the Rings trilogy.